This invention generally relates to saw chain sharpening devices and more particularly this invention relates to saw chain sharpening devices where the saw chain being sharpened is mounted on the cutting bar and the operator of a chain saw is at the job site which is frequently in the woods. This device provides for precise and accurate file sharpening of the saw chain by providing precisely aligned file guide bushings which allows the operator of the chain saw to accurately sharpen the saw chain without taking the chain saw to a shop. It is important to note that there are several devices on the market that are within the art of saw chain sharpening. A number of these devices have been patented and are described in U.S. Pat. Nos. 2,440,633; 3,005,362; 3,027,784; 3,055,238; 3,322,000; 3,670,600. The devices defined and claimed in the U.S. Pat. Nos. 3,005,362; 3,670,600; 3,905,118 and 3,322,000 are particularly designed for use in the woods and for use by the chain saw operator. Some of the prior art devices designed for use in the woods have been constructed to simply rest on the cutting bar or on the saw links or otherwise and are not secured to the chain saw. Because the device is not secured to the saw assembly, the saw teeth consequently are not filed consistently with regard to the angle across the cutting edge of the saw tooth and are not consistently filed in a direction which is about 10.degree. to 11.degree. inclined to the horizontal to the vertically directed cutting bar. Those devices designed to provide sufficient accuracy so that the saw chain is properly filed are either very difficult to use by the operator and require special set-up procedures, procedures all of which are difficult and cumbersome, especially in the woods. Also most of the devices which provide for accurate sharpening are expensive and simply not economically feasible for use by the chain saw operator. Because of the cost of these devices, it would be more realistic for the chain saw operator to simply hand file the saw without using anything other than a file. Such filing may result in a saw chain useable until it can be put in the shop for proper sharpening. There are other devices which are less expensive and which are designed for use in the field by the chain saw operator. Although these devices may be low in cost, they generally do not provide the accuracy and the control of the file resulting in a saw chain improperly filed. In summary, saw chain sharpening devices that are currently available and useable in the woods by the chain saw operator are either expensive, cumbersome and difficult to use or they are low cost but fail to provide the control and the positioning of the file in order to properly file the saw chain according to the manufacturer's specifications. Accordingly, it is an object of this invention to provide a saw chain sharpening device which is simple to use and with no adjustments to be made by the chain saw operator. Another object of this invention is to provide a low cost, highly reliable and long lasting device which is useable by the chain saw operator at the work place. A still further object of the invention is to provide a device which is not only simple to use by physically small, light weight and portable. Yet another object of the invention is to provide a device which when straddle mounted on the chain saw and affixed to the cutting bar provides a file guide means for very accurately controlling the file angle relative to the saw chain tooth being filed. Yet another object of the invention is to provide a device having hardened steel bushings diammetrically opposed and having at least one pair of these bushings angularly positioned relative to the cutting bar and the saw chain so that the operator can file sharpen the saw chain to the manufacturer's specifications. The at least one pair of bushings being diammetrically opposed on an axis which is about 30.degree. from an axis which would be normal to the saw chain travel direction that direction being along the cutting bar from the motor end toward the tip end on the top edge of the bar. Further objects and uses of the invention will become apparent after reading the following detailed specification.